Device for shaving hair having a cutting member with a periodical motion

ABSTRACT

The invention relates to a device ( 1 ) for shaving hair ( 93 ) and to a shaving head ( 9 ) used therein. The shaving head ( 9 ) has at least one cutting member ( 17, 19 ) having a cutting edge ( 23 ) and a cutting direction (X), and the device has an actuator ( 29 ) for effecting a periodical motion of said cutting member relative to a base portion ( 3 ) of the device. According to the invention said periodical motion is effected in an imaginary plane which extends transversely to the cutting edge ( 23 ) and which has a first motion portion ( 89 ) and a second motion portion ( 91 ) following the first motion portion. The first motion portion is mainly directed in the cutting direction (X), and the second motion portion is mainly directed opposite to the cutting direction and is closer to the skin ( 93 ) than the first motion portion. Said periodical motion results in a reduced risk of skin irritations and skin injuries and provides a smooth shaving result. In a particular embodiment the periodical motion is an elliptical motion with a major axis ( 85 ) extending mainly in the cutting direction (X) and with a minor axis ( 87 ) extending mainly in a Z-direction which is perpendicular to the cutting direction and the cutting edge ( 23 ).

The invention relates to a device for shaving hair, comprising a baseportion having a grip, at least one cutting member having a cutting edgeand a cutting direction, and an actuator for effecting a periodicalmotion of the cutting member relative to the base portion.

The invention further relates to a shaving head suitable for use in adevice for shaving hair, said shaving head comprising at least onecutting member having a cutting edge and a cutting direction, and acoupling member by means of which the shaving head can be coupled to abase portion of said device, said base portion comprising an actuatorfor effecting a periodical motion of the cutting member relative to thebase portion.

A device for shaving hair of the kind mentioned in the openingparagraphs and comprising a shaving head of the kind mentioned in theopening paragraphs is known from U.S. Pat. No. 2,054,418. The shavinghead of the known device comprises a blade-shaped cutting member. Theactuator of the known device comprises an electric motor having a shaftto which a flywheel is eccentrically secured. The flywheel is arrangedin the shaving head of the known device and is substantially parallel tothe main surfaces of the cutting member. The shaft is supported by twobearings, one of which is also arranged in the shaving head. Duringoperation, when the flywheel is rotated by the motor, the flywheelexerts periodical forces on the bearings. Via the bearing arranged inthe shaving head, said forces are transmitted to the shaving head andeffect a circular periodical motion of the shaving head and of thecutting member mounted therein relative to the base portion. Thecircular periodical motion of the cutting member takes placesubstantially in an imaginary plane parallel to the main surfaces of thecutting member. As a result of said periodical motion of the cuttingmember, the device has an improved hair cutting action.

A disadvantage of the known device for shaving hair and of the knownshaving head used therein is that, when the shaving head is moved overthe skin in the cutting direction, the skin will bulge in front of thecutting edge as a result of the pressure, which is exerted on the skinby the cutting edge and which depends on the pressure with which theuser presses the shaving head on the skin. As a result, there is aconsiderable risk of skin irritations and skin injuries.

It is an object of the present invention to provide a device for shavinghair and a shaving head of the kinds mentioned in the opening paragraphsby means of which a good hair cutting action and a smooth shaving resultare achieved, but wherein the risk of skin irritations and skin injuriesis considerably reduced.

In order to achieve this object, a device for shaving hair in accordancewith the invention and a shaving head in accordance with the inventionare characterized in that the periodical motion is effectedsubstantially in an imaginary plane extending transversely to thecutting edge and has a first motion portion and a second motion portionfollowing the first motion portion, the first motion portion beingmainly directed in the cutting direction, and the second motion portionbeing mainly directed opposite to the cutting direction and being closerto the skin, during operation, than the first motion portion. When thedevice for shaving hair in accordance with the invention, provided withthe shaving head in accordance with the invention, is moved over theskin in the cutting direction of the cutting member, hairs are mainlycut during the first motion portions of the periodical motion of thecutting member. During the second motion portions, the velocity of thecutting member relative to the skin is relatively low and the cuttingmember even moves in a direction opposite to the cutting direction ofthe cutting member, so that the cutting member does not cut hairs andalso can not cause skin injuries. Since the second motion portions arecloser to the skin than the first motion portions, the skin will bulgenear the cutting edge mainly during the second motion portions when thecutting member cannot cause skin injuries. During the first motionportions, bulging of the skin near the cutting edge will be considerablyreduced or will even be absent or substantially absent, so that duringthe first motion portions, when the hairs are cut, the risk of skinirritations or injuries is relatively small. During the first motionportions contact between the skin and the cutting edge is maintained asa result of the elasticity of the skin. However, the pressure exerted bythe cutting edge on the skin will be relatively small during the firstmotion portions. In this manner it is achieved that during the firstmotion portions a smooth shaving result is achieved as a result of saidcontinued contact between the cutting edge and the skin, but the risk ofskin irritations and skin injuries is considerably reduced as a resultof the relatively small degree of skin bulging near the cutting edge andthe relatively small pressure exerted by the cutting edge on the skin.

An additional advantage of the invention is that, during the firstmotion portions, the cutting member has a cutting speed relative to theskin which is considerably higher than the speed at which the shavinghead is moved over the skin. This is a result of the fact that, duringthe first motion portions, the cutting member moves mainly in thecutting direction relative to the base portion. As a result, the timenecessary to cut a hair is considerably reduced, so that the time duringwhich a pulling force is exerted on the hair during cutting isrelatively short. As a result, the user experiences a relatively highlevel of shaving comfort.

A further advantage of the invention is that, when the cutting membermoves in a direction opposite to the cutting direction during the secondmotion portions, the friction forces exerted by the skin on the cuttingmember are directed in the cutting direction and thus provide a tractionforce on the shaving head in the direction in which the shaving head ismoved over the skin. During the first motion portions, said frictionforces are relatively small as a result of the relatively small pressurebetween the cutting member and the skin. The overall effect is that theshaving head can be easily moved over the skin and accordingly has goodgliding properties with respect to the skin.

A yet further advantage of the invention is that the periodical motionof the cutting member results in a stimulation of the nerves in theskin. This effect is enhanced because the periodical motion of thecutting member has a component perpendicular to the skin as a result ofthe fact that the second motion portion is closer to the skin than thefirst motion portion. As a result of said stimulation of the nerves painsensations, which occur as a result of pulling forces exerted on thehairs during cutting, will be perceived by the user to a considerablylesser extent.

A particular embodiment of a device for shaving hair in accordance withthe invention is characterized in that the periodical motion has afrequency between approximately 100 Hz and approximately 1000 Hz. It wasfound that, when the frequency of the periodical motion is within saidrange, the effects and advantages of the invention as described beforemanifest themselves to a high extent.

A further embodiment of a device for shaving hair in accordance with theinvention is characterized in that the periodical motion has a frequencyof approximately 200 Hz. It was found that, when the frequency of theperiodical motion is approximately 200 Hz, most effects and advantagesof the invention as described before manifest themselves to an optimumextent.

A particular embodiment of a device for shaving hair in accordance withthe invention is characterized in that the periodical motion is asubstantially elliptical motion having a major axis and a minor axis,the major axis being mainly directed parallel to the cutting direction.It was found that the effects and advantages of the invention asdescribed before particularly manifest themselves when the first and thesecond motion portion have a length which is considerably larger than adistance which is present between the first and the second motionportion in a direction perpendicular to the skin. By means of saidelliptical motion, such a relation between said length and said distanceis achieved in a practical manner, the first motion portion taking placein an upper part of the elliptical motion, and the second motion portiontaking place in a lower part of the elliptical motion, as seen withrespect to the skin. Such an elliptical motion can be achieved by meansof a relatively simple, practical and reliable driving mechanism andwith relatively small and gradual acceleration forces.

A further embodiment of a device for shaving hair in accordance with theinvention is characterized in that the major axis has a length betweenapproximately 0.1 mm and 0.6 mm and the minor axis has a length betweenapproximately 0.02 mm and 0.15 mm. It was found that, when the majoraxis and the minor axis of the elliptical motion have a length withinsaid ranges, the effects and advantages of the invention as describedbefore manifest themselves to a high extent.

A yet further embodiment of a device for shaving hair in accordance withthe invention is characterized in that the major axis has a length ofapproximately 0.4 mm and the minor axis has a length of approximately0.05 mm. It was found that, when the major axis of the elliptical motionhas a length of approximately 0.4 mm and the minor axis of theelliptical motion has a length of approximately 0.05 mm, most effectsand advantages of the invention as described before manifest themselvesto an optimum extent.

A further embodiment of a device for shaving hair in accordance with theinvention is characterized in that the device has a skin contact memberwhich defines an imaginary skin contact surface along which the deviceis in contact with the skin during operation, wherein the major axis andthe skin contact surface enclose an angle between approximately −30° andapproximately +30°. It was found that, when the angle enclosed by themajor axis of the elliptical motion and the skin contact surface iswithin said range, the effects and advantages of the invention asdescribed before manifest themselves to a high extent.

A yet further embodiment of a device for shaving hair in accordance withthe invention is characterized in that the major axis extendssubstantially parallel to the skin contact surface. It was found that,when the major axis of the elliptical motion extends substantiallyparallel to the skin contact surface, i.e. when the angle enclosed bythe major axis and the skin contact surface is approximately 0°, mosteffects and advantages of the invention as described before manifestthemselves to an optimum extent.

A particular embodiment of a device for shaving hair in accordance withthe invention is characterized in that the cutting member is arranged ina shaving head which is mounted to the base portion, the actuatoreffecting a periodical motion of the cutting member relative to theshaving head. In this embodiment the shaving head is stationary relativeto the base portion, and the actuator effects a periodical motion of thecutting member relative to the shaving head and the base portion. Anadvantage of this embodiment is that the position of the skin relativeto the periodical motion of the cutting member and, as a result, thepositions of the first and the second motion portion relative to theskin are well defined by the stationary shaving head, so that theeffects and advantages of the invention manifest themselves to anoptimum extent. In addition, the mass of the portion of the device whichperforms the periodical motion is limited, so that the necessary drivingforces and also the reaction forces experienced by the user are limited.

A particular embodiment of a device for shaving hair in accordance withthe invention is characterized in that the cutting member is mounted ina shaving head which is mounted to the base portion, the actuatoreffecting a joint periodical motion of the shaving head and the cuttingmember relative to the base portion. In this embodiment the cuttingmember is stationary relative to the shaving head, and the actuatoreffects a joint periodical motion of the shaving head and the cuttingmember mounted therein relative to the base portion. An advantage ofthis embodiment is that the structure of the shaving head and thecutting member mounted therein is relatively simple, because the drivingmechanism can be mainly arranged outside the shaving head.

A particular embodiment of a device for shaving hair in accordance withthe invention is characterized in that the device is provided with atleast a first cutting member and a second cutting member, wherein theactuator effects a first periodical motion of the first cutting memberand a second periodical motion of the second cutting member, and whereinat least one of the two motion portions of the first periodical motionand of the second periodical motion have different parameters. In suchan embodiment with two or more separate cutting members arranged in asingle shaving head, the contribution of each individual cutting memberto the overall shaving performance of the shaving head is specific anddifferent from the contribution(s) of the other cutting member(s). Sincein this embodiment the periodical motions of the cutting members havemutually different parameters, the parameters of the periodical motionof each individual cutting member can be optimized in such a manner thateach individual cutting member has an optimum contribution to theoverall shaving performance of the shaving head. In this manner theoverall shaving performance of the shaving head is further improved.

A further embodiment of a device for shaving hair in accordance with theinvention is characterized in that the cutting member is mounted to acarrier which is driven by the actuator via a transmission comprising afirst and a second eccentric member which are driven by the actuator atequal rotational speeds about separate axes of rotation extendingparallel to the cutting edge, said first eccentric member having a fixedposition relative to the carrier in a direction parallel to the majoraxis and a free position relative to the carrier in a direction parallelto the minor axis, and said second eccentric member having a freeposition relative to the carrier in a direction parallel to the majoraxis and a fixed position relative to the carrier in a directionparallel to the minor axis. In this manner, a simple, compact, accurate,and reliable driving mechanism is obtained to effect an ellipticalmotion of the cutting member relative to the shaving head.

Embodiments of a device for shaving hair in accordance with theinvention and of a shaving head in accordance with the invention will bedescribed in the following with reference to the drawings, in which

FIG. 1 schematically shows a device for shaving hair according to theinvention, which is provided with a shaving head according to theinvention,

FIG. 2 schematically shows the shaving head of the device of FIG. 1,

FIG. 3 is a schematic side view of the shaving head of the device ofFIG. 1,

FIG. 4 shows in detail a periodical elliptical motion of a cuttingmember of the shaving head of FIG. 2,

FIG. 5A schematically shows a first motion portion of the ellipticalmotion of FIG. 4,

FIG. 5B schematically shows a second motion portion of the ellipticalmotion of FIG. 4, and

FIG. 6A, 6B, 6C show alternative periodical motions of a cutting memberof a shaving head in accordance with the invention.

FIG. 1 schematically shows a device 1 for shaving hair according to theinvention. The device 1 comprises a base portion 3, which comprises anelongate hollow cylindrical body 5 in the embodiment shown. The body 5has a grip 7 by means of which the user can hold the device 1 duringoperation. The device 1 further comprises a shaving head 9 according tothe invention having two side portions 11 and 13 and a bottom portion 15mutually connecting the side portions 11, 13. The side portions 11, 13are connected to the body 5 via a coupling member 16. In the embodimentshown, the shaving head 9 can be released from the coupling member 16and from the body 5 by means of a mechanism not shown in FIG. 1, so thatthe shaving head 9, when worn out, can be removed from the body 5 and anew shaving head can be coupled to the body 5. It is noted, however,that the invention also covers embodiments wherein the shaving headcannot be released from the base portion.

In the embodiment shown in FIG. 2 the shaving head 9 comprises a firstcutting member 17 and a second cutting member 19. As shown in FIG. 3,the cutting members 17, 19 each have a blade-shaped metal carrier 21 onwhich a straight cutting edge 23 extending substantially parallel to aY-direction is provided. FIG. 1, FIG. 2 and FIG. 3 further show acutting direction X of the cutting members 17, 19, i.e. a direction inwhich the shaving head 9 is to be moved over a skin to be shaved inorder to cut hairs present on the skin. Near each of the side portions11, 13 the cutting members 17, 19 are mounted to a plate-shaped carrier25 by means of mounting members 27. The carriers 25 are coupled to theside portions 11, 13 in a manner to be described in detail in thefollowing. It is noted that in FIG. 2 and FIG. 3 only the carrier 25,which is present near the side portion 11, is visible because a coverplate 28 of the side portion 11, which is visible in FIG. 1, is notshown in FIG. 2 and FIG. 3. However, a similar carrier is present nearthe side portion 13. It is further noted that the invention also coversembodiments in which the shaving head of the device comprises adifferent number of cutting members, for example only one cutting memberor three cutting members.

As shown in FIG. 1 and FIG. 2 an actuator 29 is arranged in the hollowcylindrical body 5. In the embodiment shown the actuator 29 comprises anelectrical motor 31 having a rotatable output shaft 33. In theembodiment shown the output shaft 33 is releasibly coupled to an inputshaft 35 of the shaving head 9 by means of a coupling member 37, so thatthe output shaft 33 can be uncoupled from the shaving head 9 when theshaving head 9 is released from the base portion 3. The shaving head 9comprises a gear system 39, which is provided with conical gear wheelsnot shown in FIG. 1 and FIG. 2 for converting a rotation of the inputshaft 35 into a rotation of a main shaft 41 of the shaving head 9, whichis rotatably journalled in the side portions 11 and 13 and extendssubstantially parallel to the cutting edges 23.

As shown in FIG. 3, near each side portion 11, 13 the main shaft 41carries a first gear wheel 43 which is concentrically mounted to themain shaft 41. Thus the first gear wheel 43 is rotatable about a firstaxis of rotation 45 coinciding with a central axis of the main shaft 41.Near each side portion 11, 13 a second gear wheel 47 and a third gearwheel 49 are journalled so as to be rotatable about, respectively, asecond axis of rotation 51 and a third axis of rotation 53 bothextending parallel to the first axis of rotation 45. Near each sideportion 11, 13 the second gear wheel 47 and the third gear wheel 49 bothengage with the first gear wheel 43. The first, second and third gearwheels 43, 47, 49 have equal diameters and an equal number of teeth, sothat the second and third gear wheels 47, 49 are driven by the firstgear wheel 43 at a rotational speed equal to the rotational speed of thefirst gear wheel 43.

The first, second and third gear wheels 43, 47, 49 are each providedwith a circularly cylindrical eccentric member 55, 57, 59 on a sidefacing away from the main shaft 41. The eccentric member 55 is providedon the first gear wheel 43 at a distance A from the first axis ofrotation 45, while the eccentric members 57 and 59 are provided on thesecond and third gear wheels 47, 49 at a distance B from the second andthird axes of rotation 51, 53, said distance B being considerablysmaller than said distance A. The eccentric member 55 of the first gearwheel 43 is arranged with substantially no play in a circular opening 61of a first plate-shaped transmission member 63, while the eccentricmembers 57 and 59 of the second and third gear wheels 47 and 49 arearranged with substantially no play in, respectively, a circular opening65 of a second plate-shaped transmission member 67 and a circularopening 69 of a third plate-shaped transmission member 71. The firsttransmission member 63 is provided in a first opening 73 of the carrier25, the first transmission member 63 having substantially no playrelative to said first opening 73 in the cutting direction X and beingfree to move in said first opening 73 in a Z-direction perpendicular tothe cutting direction X and the Y-direction. Likewise, the second andthird transmission members 67 and 71 are provided, respectively, in asecond opening 75 and in a third opening 77 of the carrier 25. However,the second and third transmission members 67 and 71 are free to move insaid second and third openings 75, 77 in the cutting direction X andhave substantially no play relative to said second and third openings75, 77 in the Z-direction. As a result, the eccentric member 55 of thefirst gear wheel 43 has a fixed position relative to the carrier 25 inthe cutting direction X and a free position relative to the carrier 25in the Z-direction, while the eccentric members 57 and 59 of the secondand third gear wheels 47, 49 each have a free position relative to thecarrier 25 in the cutting direction X and a fixed position relative tothe carrier 25 in the Z-direction.

During operation the eccentric members 55, 57, 59 are driven by theactuator 29 at equal rotational speeds about, respectively, the firstaxis of rotation 45, the second axis of rotation 51, and the third axisof rotation 53 extending parallel to the cutting edges 23. As a resultof the fact that the distance A is considerably larger than the distanceB, said rotations of the eccentric members 55, 57, 59 effect aperiodical substantially elliptical motion of the carrier 25 and of thecutting members 17, 19 mounted thereto relative to the shaving head 9and relative to the base portion 3, said elliptical motion having amajor axis, which extends in the cutting direction X and has a lengthequal to 2*A, and a minor axis, which extends in the Z-direction and hasa length equal to 2*B. The transmission formed by the input shaft 35,the gear system 39, the main shaft 41, the gear wheels 43, 47, 49, theeccentric members 55, 57, 59, the transmission members 63, 67, 71, andthe carriers 25 constitutes a simple, compact, accurate, and reliabledriving mechanism for effecting said elliptical motion of the cuttingmembers 17, 19 relative to the shaving head 9 and the base portion 3.

As further shown in FIG. 2 and FIG. 3, the shaving head 9 comprises askin stretching member 79 made of rubber, which is mounted to the bottomportion 15 of the shaving head 9 in front of the cutting members 17, 19,as seen in the cutting direction X. When the shaving head 9 is movedover the skin in the cutting direction X, the skin stretching member 79moves over the skin in front of the cutting members 17, 19, so that theskin present before the cutting members 17, 19 is stretched to someextent by the friction force exerted by the skin stretching member 79 onthe skin. Behind the cutting members 17, 19, as seen in the cuttingdirection X, a skin supporting member 81 is mounted to the bottomportion 15 of the shaving head 9. The skin stretching member 79 and theskin-supporting member 81 both extend in directions parallel to theY-direction and, accordingly, parallel to the cutting edges 23. The skinstretching member 79 and the skin supporting member 81 together form askin contact member of the shaving head 9, which defines an imaginaryskin contact surface 83 extending parallel to the cutting direction Xand parallel to the Y-direction, along which skin contact surface 83 theshaving head 9 is in contact with the skin during operation.

Since the major axis of the elliptical motion of the cutting members 17,19 described before extends in the X-direction and the minor axis ofsaid elliptical motion extends in the Z-direction, i.e. perpendicular tothe skin contact surface 83, the periodical elliptical motion of thecutting members 17, 19 is effected in an imaginary plane which extendsperpendicularly to the Y-direction, i.e. perpendicularly to the cuttingedges 23. The path of the elliptical motion of the cutting members 17,19 with respect to the skin contact surface 83 and with respect to thecutting direction X is shown in detail in FIG. 4, wherein the major andminor axes are indicated with reference numbers 85 and 87, respectively.As shown in FIG. 3 and FIG. 4, the rotational direction R of the mainshaft 41 is such that in a first motion portion 89 of the ellipticalmotion, i.e. an upper part of the elliptical motion wherein the cuttingmembers 17, 19 are least close to the skin, the cutting members 17, 19move mainly in the cutting direction X, while in a second motion portion91 of the elliptical motion, i.e. a lower part of the elliptical motionwherein the cutting members 17, 19 are closest to the skin, the cuttingmembers 17, 19 move mainly in a direction opposite to the cuttingdirection X. In the embodiment shown the second motion portion 91 isapproximately situated in the skin contact surface 83, but this is not anecessity for a proper functioning of the device 1. Accordingly, theelliptical motion may be situated completely above the skin contactsurface 83, as seen with respect to the skin, but may also be situatedpartially or even completely below the skin contact surface 83,depending on the other parameters of the elliptical motion as describedin the following. In each case, however, the second motion portion 91,wherein the cutting members 17, 19 move mainly in a direction oppositeto the cutting direction X, should be closer to the skin than the firstmotion portion 89, wherein the cutting members 17, 19 move mainly in thecutting direction X.

The effect of the elliptical motion of the cutting members 17, 19 is asfollows. When the shaving head 9 is moved over the skin in the cuttingdirection X, the user will slightly press the shaving head 9 against theskin. As a result, a pressure is exerted by the cutting edges 23 of thecutting members 17, 19 on the skin, so that the skin will bulge near thecutting edges 23. During the elliptical motion of the cutting members17, 19 a maximal skin bulging rate and a maximal pressure of the cuttingedges 23 will be present during the second motion portions 91 when thecutting members 17, 19 are closest to the skin 93. This situation isschematically shown in FIG. 5B. During the first motion portions 89, asschematically shown in FIG. 5A, the skin bulging rate is considerablysmaller, or will even be negligible or zero, depending on the parametersof the elliptical motion as described in the following. When the cuttingmembers 17, 19 move from the second motion portion 91 to the firstmotion portion 89, the cutting members 17, 19 move away from the skin 93and the skin 93 will follow the cutting members 17, 19 and maintain incontact with the cutting edges 23 as a result of its elasticity. As aresult of the viscous properties of the skin 93, however, the pressureexerted by the skin 93 on the cutting edges 23 will strongly decreaseand, as a result, the pressure exerted by the cutting edges 23 on theskin 93 will be relatively small or even zero during the first motionportions 89. Accordingly it was found that, as a result of the viscousand elastic properties of the skin 93, the pressure exerted by the useron the shaving head 9 mainly determines the skin bulging rate and thepressure of the cutting edges 23 on the skin 93 during the second motionportions 91, while, during the first motion portions 89, the skinbulging rate and the pressure of the cutting edges 23 on the skin 93 arerelatively small and are influenced to a considerably lesser extent bythe pressure exerted by the user.

When the shaving head 9 is moved over the skin 93 in the cuttingdirection X, the velocity of the cutting members 17, 19 relative to theskin 93 is the sum of the velocity at which the user moves the shavinghead 9 in the cutting direction X, and the velocity at which the cuttingmembers 17, 19 move relative to the base portion 3 according to theelliptical motion. As a result, the cutting members 17, 19 will have arelatively high velocity in the cutting direction X relative to the skin93 during the first motion portions 89, and a relatively low velocity inthe cutting direction X relative to the skin 93, or even a velocity inthe opposite direction, during the second motion portions 91. As aresult, hairs present on the skin 93 are mainly cut during the firstmotion portions 89. During the second motion portions 91 no hairs arecut by the cutting members 17, 19, provided that the frequency andamplitude of the elliptical motion are sufficiently high. Since the skinbulging rate and the pressure exerted by the cutting edges 23 on theskin 93 are relatively small during the first motion portions 89, therisk of skin irritations and skin injuries is relatively small. Duringthe second motion portions 91, the velocity of the cutting members 17,19 relative to the skin 93 is relatively small and the cutting membersmay even move in a direction opposite to the cutting direction X, sothat the risk of skin irritations and skin injuries is also relativelysmall or even zero. As a result, the risk of skin irritations and skininjuries as a result of the use of the device 1 in accordance with theinvention is relatively small. Since the skin 93 maintains in contactwith the cutting edges 23 during the first motion portions 89, thedevice 1 according to the invention provides a smooth shaving result anda good shaving performance.

The additional advantages of the invention described hereinbefore in thedescription of the invention will be readily understandable by means ofthe foregoing detailed description of the device 1. A further advantageof the invention is that, depending on the frequency and the amplitudeof the elliptical motion of the cutting members 17, 19 and on thevelocity with which the user moves the shaving head 9 over the skin 93,there will be an overlap between the skin portions which aresuccessively shaved during a number of successive first motion portions89 of the elliptical motion. As a result each skin portion is treatedmore than once by the cutting members 17, 19 during a single continuousmotion of the shaving head 9 over the skin 93, so that the shaving head9 is very effective.

In the embodiment of the device 1 and the shaving head 9 according tothe invention as described before, the periodical elliptical motion ofthe cutting members 17, 19 has a frequency of approximately 200 Hz. Thedistance A is approximately 0.2 mm and the distance B is approximately0.025 mm, so that the major axis 85 of the elliptical motion has alength of approximately 0.4 mm and the minor axis 87 of the ellipticalmotion has a length of approximately 0.05 mm. Furthermore, the majoraxis 85 of the elliptical motion extends substantially parallel to theskin contact surface 83. It was found that, with the above-mentionedvalues for the parameters of the elliptical motion of the cuttingmembers 17, 19, the effects and advantages of the invention manifestthemselves to an optimum extent. However, the invention is not limitedto embodiments wherein the parameters of the elliptical motion of thecutting members 17, 19 have the above-mentioned values. It was foundthat most effects and advantages of the invention manifest themselves toa high extent if the frequency of the elliptical motion is betweenapproximately 100 Hz and approximately 1000 Hz, if the major axis 85 ofthe elliptical motion has a length between approximately 0.1 mm and 0.6mm, if the minor axis 87 of the elliptical motion has a length betweenapproximately 0.02 mm and 0.15 mm, and if the major axis 85 of theelliptical motion and the skin contact surface 83 enclose an anglebetween approximately −30° and +30°. It is noted that in the foregoingthe expression “approximately” intends to indicate a margin of at most5% of the indicated values. It is however noted that the invention alsocovers embodiments in which some of the above mentioned parameters ofthe elliptical motion have values outside the indicated ranges, and theskilled person will be able to find other suitable values for theseparameters by means of experiments.

As described in the foregoing, the periodical elliptical motion of thecutting members 17, 19 can be achieved by means of a relatively simpleand reliable driving mechanism. The acceleration forces to be exerted onthe cutting members 17, 19 are relatively small and gradual, so that theuser hardly experiences inconvenient reaction forces of the drivingmechanism. However, the invention is not limited to embodiments in whichan elliptical or substantially elliptical motion of the cutting membersis effected. In general, the above-mentioned effects and advantages ofthe invention manifest themselves if a periodical motion of the cuttingmembers is effected relative to the base portion in an imaginary planeor mainly in an imaginary plane which extends transversely to thecutting edge, and wherein said motion has a first motion portion mainlydirected in the cutting direction of the cutting member and a secondmotion portion following the first motion portion and mainly directedopposite to the cutting direction, said second motion portion beingcloser to the skin than said first motion portion. In the foregoing theexpression “transversely to” is not limited to “perpendicularly to”, butintends to indicate that said imaginary plane has a main directionperpendicular to the cutting edge and may have an additional minordirection component in another direction. In a similar manner, theexpression “mainly directed” intends to indicate that the relevantmotion portion has a main motion component in or opposite to the cuttingdirection, but that an additional minor motion component may be presentin another direction. It was further found that the effects andadvantages of the invention particularly manifest themselves when saidfirst and second motion components have lengths which are considerablylarger than a distance which is present between said first and secondmotion portions in a direction perpendicular to the skin. Theabove-described general properties of a periodical motion according tothe invention are readily achieved by means of an elliptical motion, butthe skilled person will be able to find alternative periodical motionswhich also have such general properties and will be able to find drivingmechanisms to effect such alternative periodical motions. An example ofsuch an alternative periodical motion is an approximately rectangularmotion in an imaginary plane transverse to the skin with first andsecond motion portions 89′, 91′ as shown in FIG. 6A, a substantiallytriangular motion wherein the first and second motion portions 89″, 91″enclose a relatively small angle as shown in FIG. 6B, or an oval motionwith first and second motion portions 89′″, 91′″ as shown in FIG. 6C. Itis noted, however, that the effects and advantages of the invention alsomanifest themselves to some degree when said first and second motioncomponents have lengths which are comparable with the distance which ispresent between said first and second motion portions in a directionperpendicular to the skin. Accordingly, the invention also coversembodiments in which the periodical motion is, for example, a circularmotion, in which case a relatively simple driving mechanism can be used,or approximates a square motion.

In the device 1 and in the shaving head 9 as described before, theshaving head 9 is stationary relative to the base portion 3, and theactuator 29 effects a periodical motion of the cutting members 17, 19relative to the shaving head 9 and the base portion 3. An advantage isthat the position of the skin 93 relative to the periodical motion ofthe cutting members 17, 19 and, in particular, the positions of thefirst and second motion portions 89, 91 of the elliptical motionrelative to the skin are well defined by the stationary skin contactsurface 83, so that the effects and advantages of the invention canmanifest themselves to an optimum extent. In addition, the total mass ofthe periodically moving portions of the shaving head 9 is considerablylimited, so that the necessary driving forces and the reaction forcesexperienced by the user holding the device 1 are considerably limited.However, the invention also covers embodiments in which the necessaryperiodical motion of the cutting member relative to the base portion ofthe device is achieved in that the actuator effects a periodical motionof the entire shaving head including the cutting member mounted therein.In such an embodiment the cutting member is mounted in a stationary orsubstantially stationary position in the shaving head, so that thestructure of the shaving head and the cutting member mounted therein isrelatively simple. Such an alternative embodiment may be advantageous inembodiments of the device according to the invention wherein the shavinghead can be uncoupled from the base portion and exchanged for a newshaving head. In such an embodiment the driving mechanism, which effectsthe periodical motion of the entire shaving head, can be mainly arrangedoutside the shaving head, so that the costs of the exchangeable portionof the device are limited. Such an alternative embodiment is not shownin the drawings, but the skilled person will be able to find a suitablestructure and a suitable driving mechanism for such an alternativeembodiment.

In the device 1 and in the shaving head 9 as described before thecutting members 17, 19 are jointly mounted to the carriers 25, so thatthe cutting members 17, 19 are subjected to identical periodicalmotions. The invention also covers embodiments of a device for shavinghair and of a shaving head for use therein, wherein the shaving head hastwo or more cutting members, wherein a first one of said cutting membersis subjected to a first periodical motion and a second one of saidcutting members is subjected to a second periodical motion, and whereinat least one of the motion portions of said first and second periodicalmotions have mutually different parameters. Such an alternativeembodiment of a device and a shaving head according to the invention isnot shown in the drawings, but the skilled person will be able to find asuitable structure and a suitable driving mechanism for such analternative embodiment. A suitable driving mechanism may for example beobtained by providing in FIG. 3 a further carrier adjacent to thecarrier 25, and by mounting one of the cutting members 17, 19 to saidfurther carrier instead of to the carrier 25. The further carrier may bedriven by three additional eccentric members, which are coupled to thegear wheels 43, 47, 49 as axial extensions of the eccentric members 55,57, 59, but which have radial and tangential positions relative to thegear wheels 43, 47, 49 which differ from the radial and tangentialpositions of the eccentric members 55, 57, 59 relative to the gearwheels 43, 47, 49. Since in such an alternative embodiment theperiodical motions of the cutting members have mutually differentparameters, the parameters of the periodical motion of each individualcutting member can be optimized in such a manner that each individualcutting member has an optimum contribution to the overall shavingperformance of the shaving head. In this way the overall performance ofthe shaving head is further improved.

1. A device for shaving hair, comprising a base portion having a grip,at least one cutting member having a cutting edge and a cuttingdirection, and an actuator for effecting a periodical motion of thecutting member relative to the base portion, characterized in that theperiodical motion is effected substantially in an imaginary planeextending transversely to the cutting edge and has a first motionportion and a second motion portion following the first motion portion,the first motion portion being mainly directed in the cutting direction,and the second motion portion being mainly directed opposite to thecutting direction and being closer to the skin, during operation, thanthe first motion portion.
 2. A device as claimed in claim 1,characterized in that the periodical motion has a frequency betweenapproximately 100 Hz and approximately 1000 Hz.
 3. A device as claimedin claim 2, characterized in that the periodical motion has a frequencyof approximately 200 Hz.
 4. A device as claimed in claim 1,characterized in that the periodical motion is a substantiallyelliptical motion having a major axis and a minor axis, the major axisbeing mainly directed parallel to the cutting direction.
 5. A device asclaimed in claim 4, characterized in that the major axis has a lengthbetween approximately 0.1 mm and 0.6 mm and the minor axis has a lengthbetween approximately 0.02 mm and 0.15 mm.
 6. A device as claimed inclaim 5, characterized in that the major axis has a length ofapproximately 0.4 mm and the minor axis has a length of approximately0.05 mm.
 7. A device as claimed in claim 4, characterized in that thedevice has a skin contact member which defines an imaginary skin contactsurface along which the device is in contact with the skin duringoperation, wherein the major axis and the skin contact surface enclosean angle between approximately −30° and approximately +30°.
 8. A deviceas claimed in claim 7, characterized in that the major axis extendssubstantially parallel to the skin contact surface.
 9. A device asclaimed in claim 1, characterized in that the cutting member is arrangedin a shaving head which is mounted to the base portion, the actuatoreffecting a periodical motion of the cutting member relative to theshaving head.
 10. A device as claimed in claim 1, characterized in thatthe cutting member is mounted in a shaving head which is mounted to thebase portion, the actuator effecting a joint periodical motion of theshaving head and the cutting member relative to the base portion.
 11. Adevice as claimed in claim 1, characterized in that the device isprovided with at least a first cutting member and a second cuttingmember, wherein the actuator effects a first periodical motion of thefirst cutting member and a second periodical motion of the secondcutting member, and wherein at least one of the two motion portions ofthe first periodical motion and of the second periodical motion havedifferent parameters.
 12. A device as claimed in claim 4, characterizedin that the cutting member is mounted to a carrier which is driven bythe actuator via a transmission comprising a first and a secondeccentric member which are driven by the actuator at equal rotationalspeeds about separate axes of rotation extending parallel to the cuttingedge, said first eccentric member having a fixed position relative tothe carrier in a direction parallel to the major axis and a freeposition relative to the carrier in a direction parallel to the minoraxis, and said second eccentric member having a free position relativeto the carrier in a direction parallel to the major axis and a fixedposition relative to the carrier in a direction parallel to the minoraxis.
 13. A shaving head suitable for use in a device for shaving hair,said shaving head comprising at least one cutting member having acutting edge and a cutting direction, and a coupling member by means ofwhich the shaving head can be coupled to a base portion of said device,said base portion comprising an actuator for effecting a periodicalmotion of the cutting member relative to the base portion, characterizedin that the periodical motion is effected substantially in an imaginaryplane extending transversely to the cutting edge and has a first motionportion and a second motion portion following the first motion portion,the first motion portion being mainly directed in the cutting direction,and the second motion portion being mainly directed opposite to thecutting direction and being closer to the skin, during operation, thanthe first motion portion.